The present invention relates to a combination lock which is applied to various opening/closing parts for safes, lockers, strong rooms and others.
Conventionally, in a locker for rent, for example, a lock which is opened and closed by a peculiar key is installed on a locker basis.
The user of a locker is to carry the key, and therefore accidents of theft due to loss or dishonest use of a locker key have happened frequently.
These troubles can be eliminated by applying a code lock using numerals 1-0 which requires no key. However, in the conventional code locks, numerals used for unlocking are determined by a mechanical structure on a lock basis. Numerals used for unlocking can be changed by adjusting the mechanical structure inside the lock, but in order to change the numerals for unlocking, a lever or a pin has to be operated from the side surface or the rear surface of the lock main body, and in the case of the locker used always by many unspecified persons, it is impossible to change the numerals for unlocking every time of use. Also, in the case where no numerals are changed, a problem remains that unlocking is made by another person by memorizing the numerals.
To accommodate for this problem, recently electric type code locks have appeared.
In the electric type code lock, the user of a locker touch-operates keys 1-0 on a key-board disposed on a lock case to determine arbitrary numerals for unlocking while watching digital numerals appearing on a display, and thereafter by locking a locking mechanism, the numerals are stored in an electronic circuit in the lock as numerals for unlocking, thereby the locked stated being kept.
However, in the case of the electric type code lock, a problem remains that should a power failure occur even for an instant, the numerals for unlocking stored in the electronic circuit go wrong or be lost. Also, the electric type code lock has disadvantages that it not only consumes electric power all the time but also the price of the lock becomes expensive as much as about 100,000 per unit when the installation cost is included.